Position – What decision making ability does your position within society allow? What can you directly influence?
Power – What can you physically overpower?
Influence – What can you convince and persuade others to do?

Some follow up: Focus on what you can, and not on what you can’t. Don’t make decisions that you’re not in a position to make, it’s a waste of your time and energy. Don’t influence things you don’t have influence on. If you want to change the way someone things but you can’t talk to that person, don’t think about it. It’s a waste of time. If you don’t have the power to do something, focus on what you do have the power to do.

Focus on what options you have. Don’t get lost in options that you can see and visualize and understand but cannot pick for yourself. It is a waste of time. Be more effective by focusing on what you can actually do.